In the processing of a semiconductor work piece, those skilled in the art have long understood the problem associated with the so-called “edge effect.” More specifically, in the processing of semiconductor work pieces, where plasma is employed, it should be understood that the plasma is controlled by an electrical field where it has long been understood that the electrical field strength at the edge of the upper and lower electrodes may be effected to such a degree that there will be bent electrical field lines. This edge effect provides a non-uniform electrical field strength at the edge and consequently leads to a non-uniform density of plasma in that same region. With the presence of a non-uniformly dense plasma in that region, the peripheral edge about a semiconductor work piece is often not uniformly processed.
As semiconductor work pieces have increased in size, the edge effect has caused a decrease in the yield rate. Presently, where a 300 mm procedure is widely employed in the industry, the edge effect is causing increasingly heavier losses. Those skilled in the art have attempted to mitigate the edge effect by employing various measures. For example, and as best seen in FIG. 1, a prior art assembly is shown. In the arrangement as seen in FIG. 1, a semiconductor work piece 10 is located within a vacuum processing chamber 11 which has an upper electrode 12, and a lower electrode 13 which is spaced therefrom. The vacuum processing chamber has a chamber body 14. The upper electrode 12 is grounded through the chamber body 14. As seen in that view, there are large electric magnets 15 which are positioned around the chamber body. The vacuum processing chamber 11 also is electrically coupled to a high frequency RF generator 16, and a low frequency RF generator 17. Each of these generators is operable to supply low frequency or high frequency electrical energy to form a plasma 18 within the processing chamber 11. When the plasma 18 is formed in the chamber body 14, the electric magnets 15 are energized to form a magnetic field which controls the distribution of the electrical field in the chamber body and thereby increase the yield processing results of the vacuum processing chamber 11. As should be understood, this apparatus is relatively expensive to fabricate and further consumes a large amount of electrical energy. Still further, it has shortcomings inasmuch as its performance appears somewhat limited especially at the intersection of two magnetic fields.
Referring now to FIG. 2, another prior art assembly is illustrated which has been used to address the edge effect. Similar numbers relate to similar structure from that seen in FIG. 1. It should be understood in FIG. 2, this prior art embodiment of a vacuum processing chamber is designed in a manner whereby the upper electrode 12 is not directly grounded to the chamber body as seen in FIG. 1.
Another method to address the so-called edge effect is to adjust the gas flux being provided to the vacuum processing chamber. By adjusting the gas flux of the different gasses being supplied to generate a plasma, the correct plasma density is attempted to be achieved so as to eliminate or counteract the edge effect.
Still another method which has been employed heretofore to address the edge effect is to infuse a source of cooling water to the lower electrode thereby making the surface temperature of the semiconductor work pieces 10 different so as to influence the resulting plasma performance and adjust the uniformity of same. While these devices and methods have worked with various degrees of success, there are shortcomings attendant with their implementation. Further, the losses caused by the edge effect have not been effectively and completely eliminated thereby. In addition to the apparent shortcomings noted above, it should be understood that once a vacuum processing chamber has been manufactured, its size and the resulting electrical field formed in the vacuum processing chamber is relatively fixed. Consequently, the uniformity of the plasma becomes increasingly difficult to adjust. Consequently, in view of the many factors that might influence the distribution of an electrical field, manufacturing multiple devices which have identical electrical fields becomes increasingly difficult.
Therefore, a vacuum processing chamber and related method that substantially eliminate the edge effect in a simple and effective manner and which further can be adjusted in various fashions to reduce the cost of manufacturing and increase the yield rates for semiconductor work pieces provided from same is the subject matter of the present application.